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https://dev.mysql.com/doc/internals/en/information-schema-optimizer-trace-table.html
TRACE: The trace, in JSON format (see json.org: basically it has scalars (number, string, bool) and structures (either arrays or associative arrays)).
https://dev.mysql.com/doc/internals/en/optimizer-constant-propagation.html
Probably they should not apply for LIKE either, but that's a story for another day. Constant propagation happens in a loop, so the output from one propagation step can be input for the next step.
https://dev.mysql.com/doc/internals/en/optimizer-early-nulls-filtering.html
Suppose we have a join order such as this one: ..., tblX, ..., tblY, ... Suppose further that table tblY is accessed via ref or eq_ref access on tblY.key_column = tblX.column or, in the case of ref access using multiple key parts, via ... Here the ...
https://dev.mysql.com/doc/internals/en/optimizer-partition-selection.html
If a partitioned table is accessed in a series of index lookups (that is, using the ref, eq_ref, or ref_or_null access methods), MySQL checks to see whether it needs to make index lookups in all partitions or that it can limit access to a ...
https://dev.mysql.com/doc/internals/en/optimizer-trace-implementation.html
A trace is started by creating an instance of Opt_trace_start; information is added to this trace by creating instances of Opt_trace_object and Opt_trace_array, and by using the add() functions of those classes...
https://dev.mysql.com/doc/internals/en/optimizer-trace-system-variable.html
The optimizer_trace system variable has these on/off switches: enabled: allows to enable/disable tracing one_line: if on, the trace will have no whitespace; it's unreadable for humans but readable for JSON parsers (they ignore whitespace); the only ...
https://dev.mysql.com/doc/internals/en/optimizer-trace-testing.html
This feature is tested in mysql-test/suite/opt_trace and unittest/gunit/opt_trace-t. ...
https://dev.mysql.com/doc/internals/en/optimizer-tracing-typical-usage.html
# Turn tracing on (it's off by default): SET optimizer_trace="enabled=on"; SELECT ...; # your query here SELECT * FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE; # possibly more queries... # When done with tracing, disable it: SET ...
https://dev.mysql.com/doc/internals/en/optimizer-transpositions.html
MySQL supports transpositions (reversing the order of operands around a relational operator) for simple expressions only. In other words: WHERE - 5 = column1 becomes: WHERE column1 = -5 However, MySQL does not support transpositions where ...
https://dev.mysql.com/doc/heatwave/en/mys-hwaml-ml-metrics.html
The ML_TRAIN routine includes the optimization_metric option, and the ML_SCORE routine includes the metric option. Both of these options define a metric that must be compatible with the task type and the target data. precision_k: An Oracle ...